1. Field of the Invention
The present invention relates to nitride semiconductor devices and methods of manufacturing the same.
2. Description of the Background Art
Conventional nitride semiconductor devices are manufactured by forming and thermally processing a p electrode on a p-type contact layer and then forming a pad electrode on the p electrode (refer to, for example, Japanese Patent Nos. 3427732 and 3765246.)
Performing heat treatment in an atmosphere containing oxygen after the formation of a p electrode, as described above, induces oxidation of the p electrode, resulting in the formation of an oxide film. Forming a pad electrode on this p electrode means that a pad electrode is formed with the oxide film as an insulator present on the p electrode, so that the oxide film can cause a failure in contact between the p electrode and the pad electrode formed thereon.
Such a failure in contact between the p electrode and the pad electrode will increase the resistance between the electrodes, and for example if the nitride semiconductor device is a laser diode, there will occur an increase in the operating voltage of the laser diode and variations in electrical characteristics due to heat generation during operation. This consequently makes it difficult to provide stable operation and output within a specified temperature range. The above resistance can also be a factor in reducing yields.
It is thus desired that connectivity between the p electrode and the pad electrode be improved so as to reduce its influence on device characteristics.